Apple TV TVOS issue with Yamaha RXV2600 Receiver

Hi,

I have a Yamaha Home theatre receiver RXV260 that supports HDMI 1.1

I have the latest Apple TV (4K) and this connects to the receiver and then the receiver connects to my Sony 4k TV.

This all works fine when TVOS 10.2.2 is installed. When I upgrade to the any later version of TVOS then I get a degraded picture on the TV - areas of the screen displaying dots.

I have connected the apple TV direct to the Sony (i.e. take the receiver out of the mix) and that works fine.

So obviously something has changed in TVOS since 10.2.2 that is causing an issue with the receiver.

I was fine staying at 10.2.2 and ignoring the requests from Apple to update TVOS but now notice the new movies eg. Kingsman wont play on TVOS 10.2.2 due to HDCP errors.

Help! any suggestions gratefully appreciated

thanks